I RESTRICTED AND COMMERCIAL IN CONFIDENCE HY-TRAK 100D SERVICE MANUAL J 1 ] ] COPY NO. /S~^ DATE S./tQ.te APPROVED £)OMNITEST LIMITED The information contained herein is the property of and is supplied in confidence bv Omnitest Limited, and must not be disclosed or used either in whole or in part without the written- permission of the Company ] i ] RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l INDEX 1. SPECIFICATION AND WARRANTY 2. USER GUIDE 3. CIRCUIT DIAGRAMS 4. TEST PROCEDURE 5. ENGINEERING CHANGE NOTES RELEVANT TO HY-TRAK 100D j RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l 1. SPECIFICATION & WARRANTY 1 . 1 Specification 1.2 Limited Warranty RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 1/PAGE 1 1 . SPECIFICATION & WARRANTY 1 . 1 Specification Meter Section Ranges Accuracy Measurement Rate Display Measurement Technique 200mA 2i% 2 On., 200A ± 2% of reading ± 1 digit Approx. 3 per second 3i digit LCD Dual Slope Integration Audio Section Ranges Hy-tone Resolution Audio Output Tone Delay (Open circuit to in-range) 20mA 60mA 6 00mA 6A, 60n 4mA 40mA 400mA 4X1 250mW <50 milliseconds General Max. Voltage between Probe Tips Open Circuit Probe Voltage Probes Probe Isolation from Earth Overvoltage Protection Dimensions Weight Supply Voltage Supply Frequency Power Consumption Operating Temperature <20mV for Valid Reading Clamped to 600mV typical Removable, 4 wire Kelvin connected for accuracy >100KA to 240V ac 75mm x 220mm x 240mm (excluding handle) 1.2 Kg 230V or 115V ± 10% 50Hz - 50Hz 12VA - 70°C RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 1/PAGE 2 1 .2 Limited Warranty For a period of 90 days from the date of its purchase new and undamaged from OMNITEST LIMITED, OMNITEST LIMITED or its authorised distributors will, without charge, repair or replace at its option, this product if found by it to be defective in materials or workmanship, and if returned to OMNITEST LIMITED or its authorised distributors transportation prepaid . This limited warranty is expressly conditioned upon the product having been used only in normal usage and service in accordance with instructions of OMNITEST LIMITED and not having been altered in any way or subject to misuse, negligence or damage, and not having been repaired or attempted to be repaired by any one other than OMNITEST LIMITED or its authorised distributors. With the exception of fuse replace- ment as specifically detailed herein. EXCEPT FOR THE FOREGOING EXPRESS WARRANTY OF REPAIR OR REPLACEMENT, OMNITEST LIMITED MAKES NO WARRANTY OF ANY KIND, INCLUDING BUT NOT LIMITED TO, ANY EXPRESS OR IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE, AND OMNITEST LIMITED SHALL NOT BE LIABLE FOR ANY DAMAGES, WHETHER DIRECT OR NOT OR OTHERWISE, BEYOND REPAIR OR REPLACING THIS PRODUCT. Omnitest Limited pursue a policy of continuous development and product improvement. The specification in this document may therefore be changed without prior notice. I RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS .1 ■ 2. USER GUIDE 2 . 1 Overview 2 . 2 Operations 2 . 3 Maintenance I I RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 2 /PAGE 1 2. USER GUIDE 2 . 1 Overview The HY-TRAK 100D is the first of a new generation of state of the art short circuit locators. Its high resolution digital meter and advanced circuit design ensure an instrument of un- paralleled performance whilst maintaining an ease of use suitable to operators at all levels. Although primarily designed to locate short circuits on printed circuit boards especially multi-layer, the HY-TRAK 100D is eminently suitable for many other applications which require an accurate resistance measurement below the range of standard multimeters. Examples include checking the contact resistance of relays and switches, measuring the resistance of coils and motor windings (the HY-TRAK 100D uses a d.c. injection technique which ensures that there are no errors introduced by a.c. components) , checking for poor solder or wire-wrap joints, finding shorted output devices on bus- structured boards, etc. The instant tone feature of the HY-TRAK 100D ensures its suitability for continuity checking of cable harnesses and wire looms. The operator has the choice of using the meter or the audio tone to locate the short circuit. The lowest meter reading or the highest tone indicates the position of the short. 'Dead' shorts (less than 2% of meter f.s.d.) are indicated by a doubling of the audio tone frequency. This Hy-tone feature is unique to the HY-TRAK 100D. The HY-TRAK button introduces a super-sensitive 20 milliohm full scale tone range to produce sensible tone gradients on low resistance power tracks whilst maintaining the meter on 200 milliohm range to guarantee legible jitter- free readings. The d.c. injection (which prevents decoupling capacitors from introducing 'false' shorts as would be the case on an a.c. instrument) and the HY-TRAK range ensure that shorts between voltage planes or power tracks present no problems to the HY-TRAK 100D, which was specifically designed with this application in mind. As both probes are fully floating the HY-TRAK 100D can be used on earthed equipment without any fear of false readings due to earth loops. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 2/PAGE 2 Warning Due to the very sensitive DVM input, the HY-TRAK 100D should only be used on items that are switched off and with all capacitors discharged . If the HY-TRAK is connected in error to a voltage source the internal protection circuitry will prevent permanent damage. However, it may be necessary to replace certain fuses - see section 'Fuse Replacement'. 2.2 Operations (a) Handle Adjustment Grip the handle arms adjacent to the pivot points and press inwards. Maintaining the pressure, swivel the handle to the desired position and release. Handle will now lock in this position. (b) Initial Checks Turn the instrument on via the mains on/off switch incor- porated in the volume control. The red L.E.D. adjacent to the volume control should illuminate. A single digit 1 should appear in LCD display if the probes are not touching . (If these indications do not appear, check mains supply and internal 100mA mains fuse.) Turn volume control fully clockwise. Touch probes together. A tone should be heard. Adjust volume control to comfor- table listening level. The meter should display a reading. (The reading will not necessarily be zero. See 'Calibration' section.) (c) Calibration It is only necessary to calibrate the instrument if precise resistance readings are required. Normally, when checking for short circuits, one is looking for the minimum reading, the actual value is immaterial. (i) Allow instrument to warm up for 15 minutes with probes not touching. (ii) Set to 200 ohm range. (iii) Short probe tips together. ] RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 2/PAGE 3 (iv) Adjust 'zero' potentiometer with small screwdriver to obtain a reading of 00.0 on the LCD display. There should not be a - sign. (v) Switch to 20 ohm range. Check reading is 00.0. (vi) Reading may be typically 1-2 milliohms on 2 ohm and 200 milliohm ranges due to resistance of probe tips from Kelvin junction. Insert probes into calibration resistor sockets on rear panel. (Ensure instrument is flat on the bench. ) (vii) Set to 200 ohm range. (viii) Adjust 'cal* potentiometer to obtain reading of 100.0. (ix) Remove probes from calibrate resistor sockets. Short probes together. Check reading is still 00.0. Your HY-TRAK 100D is now calibrated to within the accuracy specification . (d) To Locate a Short Circuit on a P.C.B . (i) Set to 200 ohm range. (ii) Connect probes across suspect tracks. (iii) If tracks are shorted the LCD will display a reading. Holding one probe steady, move the other along the track until you obtain the lowest meter reading and highest tone. You are now very close to the short. Select higher sensitivity ranges, if required, to precisely locate the short. Use the HY-TRAK range on power tracks and earth planes to obtain a greater sensitivity on the audio range. (e) Resistance Measurements Ensure instrument is calibrated. Select appropriate range and read ohmic value from LCD display. If measuring suspect solder joints, contact resistance of relays, etc. do not apply excessive pressure to the probes or you may affect the resistance of the item under test. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS1 SECTION 2 /PAGE 4 J 2.3 Maintenance This will only be necessary if the instrument has been connected to a 'live' circuit. (See 'Warning') (a) Turn instrument off. (b) Disconnect from a.c. mains supply. (c) Remove 4 'posidriv' screws from base of instrument. Lift lid of case. (d) Remove fuses one at a time and check continuity. Only replace fuses with correct type and value . Using an incorrect type or value of fuse will either: (i) Affect the accuracy of the instrument, or (ii) Render the overvoltage protection inoperative, or (iii) Both (i) and (ii) above. We recommend the Schurter FSF and FST type available from Messrs Verospeed Ltd., Stansted Road, Boyatt Wood, Eastleigh, Hants. S05 4ZY. Part No. 228-23437A 100mA FST 228-23474E 200mA FSF 228-23477G 400mA FSF Or direct from Omnitest Limited. The correct value of each fuse is: Fl 100mA Antisurge Mains F2 400mA Quick Blow D.C. Inject F3 200mA Quick Blow Measurement I/P F4 400mA Quick Blow D.C. Inject F5 200mA Quick Blow Measurement I/P (e) Replace lid and tighten 4 retaining screws. (f) Reconnect to a.c. mains, switch on and verify correct operation of instrument. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l 3. CIRCUIT DIAGRAMS SHT. 1. Voltage Regulator /Constant Current SHT. 2. Current Driver Stage SHT. 3. Differential Input Amplifier SHT. 4. Audio Section SHT. 5. Decimal Point Control & L.C.D. SHT. 6. Power Supply NOTE: (a) Sheets 1. through 6. above represent the current manufactured status of the HY-TRAK 100D. (b) Sheet 3A represents the details of sheet 3. before the implementation of ECN 101. (c) Circuit diagram balloon notation used 1 ^ —l ^l i L 5 1 D 2 .IT 1 J. 1 I \ i 7— ,~ e , "9 i ■?? B Ei +ve15vRea 1-5K 27K 4-veUnr eq R5 5KMultihirn VR2 180-. 2-5W +veynn 0J1R7 15KR6 470 A Rfl TR3 2N2221A *^9jlR10 100. 1K R11 10K I R12 ri 1 I I SW2 SW3 SW4 SW5 SW6 1 R13 100*. Set Up Resistor I I C9 10^F 0v ©OMNITEST LTD. C TITLE. VOLTAGE REGULATOR/ CONSTANT CURRENT. -veUnreg ©OMNI TEST LTD. TITLE.CURRENT DRIVER STAGE. r?.r?^w ISSUE 1&20NLY ft 10 11 R25 10K1% R27 10K D9. X1 D19 N4148 200mA R19 150. ov— — 3 R26 9-1 K |— I 2K Qf^jRp VR1 (Not used by customer) ©OMNITEST LTD. TITLE. DIFFERENTIAL INPUT AMPLIFIER DWG.100D SHEET NO. 3A J L ♦4-5V .Alt OV ; Fronj-Rmel i Not on PC.B. i E vdd roh b1 91 rfh rol rfl om vinlo vin hi bp vss 02 D3 -45V IC10 4070 IC10 D15 IN4148 D16 'l * IN414R 4070 IN4148 R42 100K -45V ^xSW2 IC10 8 \^. 10 4070 - SW5 i_j i 13 ,C1 ° 3E> 4070 ©OMNI TEST LTD. TITLE.DECIMALPOINT CONTROLS LCD DWG.100D SHEETNO. | iss \/S r i 01 / I „ 1 4 e\ 5 4 A n J. : 1 __] L Zf Zf — I — I _ i i FS1 L * B 100mA 240V 50 Hz D N 0V Note. FS1= 200mA for 110V. 6 i 7 i 6 . 9 i 10 i U R3 Ji 1K 2-5W & R1 15 K rfc r ,+Zr7V ZA4-7V ::C6 • OV -+VE UNREG -+15V ►OV z &m .-, 7V -15 V — -VB UNREG ©OMNITEST LTD. TITLE. POWER SUPPLY. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l 4. TEST PROCEDURE 4 . 1 Test Equipment 4.2 Test & Set Up Procedure : i : i ~l RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4/PAGE 1 4. TEST PROCEDURE 4. 1 Test Equipment (a) DVM (Typical instrument Fluke 8024B) . (b) Bench D.C. Variable P.S.U. 0-30v. (c) Decade Resistance Box. (d) Test lamps (4 off) ITEM 1 2 PART (RADIO SPARES) RS 587-074 RS 423-790 4.2 Test & Set Up Procedure General This procedure covers the Test & Setting Up operation for both issues of the HY-TRAK 100D to date. The essential differences between the two issues are covered in the associated Engineering Change Note ECN 101. The full procedure comprises of 10 stages. It is important to note that with regard to the two issues of instrument, steps (e) through (j) are identified as (E) through (J) respectively in relation to those units produced prior to the issue of ECN 101. (a) Insulation Tests (Do not connect unit to mains.) (i) With DVM on 32 MA range: Check for coOhms between E and N, and E and L mains terminals. (ii) With DVM on 320A range: 1. Check between N and L for approx. 190D. (240V tapping) or approx. 40O-(110V setting). 2. Check for zero Ohms from mains E terminal to 0V link on centre of PCB. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4 /PAGE 2 (iii) Visually check mains tappings and orientation of transformer. The five plastic lugs on the top should be facing the rear of the PCB. (iv) Visually check that capacitor C3 has been removed from the Anders DPM module. (v) (ONLY FOR UNITS NOT INCORPORATING ECN 101) 1. Ensure IC5 position has an IC base fitted. 2. Ensure that IC's (741) are fitted to position IC3/IC4 and IC5. Experience has shown Motorola devices to give the best operation. (b) Protection Tests (Ensure that the unit is disconnected from the mains . ) (i) Remove fuses FS2-FS5. Attach the test lamps across each fuse position (4 off) . (ii) Connect probe leads. (iii) Set PSU (Bench supply) to 10V +.1V. (iv) Connect PSU -ve to HY-TRAK earth. (v) Touch one probe tip to PSU +ve, check that two lights are lit. (vi) Touch other probe tip to PSU +ve, check that the other two lights are lit. (vii) Connect PSU +ve to HY-TRAK earth and repeat steps (v) and (vi) using PSU -ve. (viii) Disconnect PSU. (ix) Replace fuses as follows: 1. FS2 and FS4 with 400mA. 2. FS3 and FS5 with 200mA. (c) D.C. Voltage Checks (i) Connect HY-TRAK to mains and turn on: LED should light. (ii) With DVM on DC Volts 32 Volt range, check: 1. Unregulated rails at ±22V ±2V on bridge rectifier 2. ±15V supplies on links at centre of PCB (±0.5V) RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4 /PAGE 3 : 3. +4.7V supplies on IC 10 pin 7 & 14 (±1.0V) (±0.5V)** 4. +0.7V supply on IC 9 pin 16 (±0.2V) (±0.1V)** ** Use these values on units not modified by ECN 101. (d) D.C. Current Inject Checks (i) With DVM on DC Volts 3200mV range, connect between ground and TR3 emitter. (This is L.H. end of large lQrt resistor at rear L.H. of switch bank.) Ensure that this voltage can be set to IV (±10mV) using VR2 (Centre pot at rear of PCB) . (ii) With DVM on DC mA 800mA range connect HY-TRAK probes to DVM probes. You should get: HY-TRAK RANGE READING ACCURACY 200/1 100UA ±1% 20A 1mA ±1% 2/v 10mA ±1% 200m.fl. 100mA ±1% HY-TRAK 100mA ±1% (e) CMRR Adjustment Not applicable after ECN 101. (f) Funct ional Checks (i) (ii) (iii) (iv) (v) Short leads together on 20QA. range. Adjust VR3 to obtain 00.0 on LCD. Connect test leads to 100a cal. resistor in rear panel of HY-TRAK. Adjust VR2 to read 100. on 200.O. range . Connect HY-TRAK leads to resistance decade box. Set to lOOn.. Ensure HY-TRAK reads 100.0 ±1.1. Set Decade box to 0n. Set HY-TRAK to 'HY-TRAK' range. Ensure reading is approx . 70 . Om/1 ±2 0mA. Set to 200mO. range. Ensure reading has not changed. Set to 2n. range. Ensure reading is .070, i.e. correlation with reading on 200mn. range ±2 LSD's. (vi) Set to 20X1 range , reading should be 0.1. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS. 1 SECTION 4 /PAGE 4 1 i On all the above ranges check correct position of decimal point. 200mn. 2a. 20/v 200/x XXX. X x.xxx XX. XX XXX. X Some leading zeros will be blanked. (vii) Set Decade box to In. Readings should be: HY-TRAK 200mTL 2n. 20/1 200TL Overrange ( 1 ) Overrange l.xyz l.xy ±2 LSD'S 1.x ±2 LSD's (viii) Set to Ida on Decade box. Reading should be: HY-TRAK 200mn 2/v 2 On. 200-n. Overrange Overrange Overrange 10. xy 10.x ±2 LSD's NOTE: Some warm up drift may occur over the first 15 minutes after switch on. (g) IC5, Select on Test On 200n range short probes together. Set volume to zero. Note reading. Turn volume to full. Reading should not vary by more than three least significant digits, preferably two. (h) Setting Up Audio Section Connect HY-TRAK to 1 On. pot. Set to 20n. range. (i) Set pot until display reads 6.0. Adjust VR4 until tone just starting to come in. Set to 6 . in. - ensure no tone . Seal VR4 with nail varnish. (ii) Set pot to 4n, set HY-TRAK to 200n. range. Adjust VR5 until you just get HY-TONE. Set pot to 4.2n - ensure no HY-TONE. Seal VR5 with nail varnish. (j) R14 S.O.T . Stay on 200n. range, ensure R14 is 4.7Kn. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4 /PAGE 5 Touch one probe to 0V - you should not get a tone. Touch other probe to 0V (after removing the first) - ensure no tone. If necessary reduce value of R14 until tone disappears for both the above tests. (k) Final Checkout Use the instrument on a PCB. Ensure that HY-TRAK audio starts at about 20mn. Ensure that 200ma tone starts at 60mn. Ensure that HY-TONE starts at 2% of FSD, i.e. 4m/ton 200mn. range. Ensure that you get progressive tone slide and that tone quality is good. Check ranges all function. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4 /PAGE 6 (E) CMRR Adjustment (BEFORE ECN 101 ONLY) Disconnect standard HY-TRAK leads. Connect CMRR leads. Connect to PSU (multiturn side) observing conventional colour code of polarity. Select PSU 0-1 5V range and set to 0V ±20mV. (i) Set HY-TRAK DPM reading to 00.0 (20CUX range) using VR3 (zero) pot. Set PSU to 1.000V ±50mV. Set HY-TRAK DPM to 00.0 using VRl (CMRR) pot. Reset PSU to 0V ±20mV, check HY-TRAK DPM still 00.0. If not goto (i) and keep repeating procedure until DPM reads at both 0V and IV. Seal VRl (CMRR) pot using nail varnish. Remove CMRR leads. Reconnect standard test leads. (F) Function Checks (BEFORE ECN 101 ONLY) (i) Connect standard test leads to 100a cal. resistor in rear panel of HY-TRAK. Adjust HY-TRAK DPM to read 100.0 on 20On. range. (ii) Connect HY-TRAK leads to resistance decade box. Set to 100n. Ensure HY-TRAK reads 100.0 ±1.1. ■ (iii) Set Decade box to 0n.. Set HY-TRAK to 'HY-TRAK' range. Ensure reading is approx. 70.0mil±10ma. (iv) Set to 200mA. range. Ensure reading has not changed. (v) Set to 2A range. Ensure reading is .070, i.e. correlation with reading on 200mA range ±2 LSD's. (vi) Set to 20n range. Reading should be approx. 0.07. (vii) Set to 200a range, reading should be 0.1. On all the above ranges check correct position of decimal point. 200mA 2a 20/v 200n. xxx. x x.xxx xx. xx xxx.x Some leading zeros will be blanked. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4/PAGE 7 (viii) Set Decade box to La. Readings should be: HY-TRAK Over range (1 ) 200mn Overrange 2a. 1 . xyz 20a l.xy ±2 LSD'S 200rv 1.x ±2 LSD's (ix) Set to 100- on Decade box. Readings should be: HY-TRAK Overrange 200mA Overrange 2a Overrange 20tv 10. xy 200a 10. x ±2 LSD's NOTE: Some warm up drift may occur over the first 15 minutes after switch on. (G) IC3, IC4, IC5, Select on Test (BEFORE ECN 101 ONLY) On any HY-TRAK range short probes together. Set volume to zero. Note reading. Turn volume to full. Reading should not vary by more than three least significant digits, preferably two. If it does, try different IC3's, IC4's and IC5*s until you find a suitable set. This problem is solved by the implementation of ECN 101. NOTE: In theory, changing IC3, 4 and 5 should not change the CMRR setting. In practice, it is worth going over section (E) (i) again. (H) Setting Up Audio Section (BEFORE ECN 101 ONLY) Reconnect HY-TRAK to resistance decade box. Set to 200a range . (i) Set decade box to 60ji. Adjust VR4 until tone just starting to come in. Set to 6 La - ensure no tone. Seal VR 4 with nail varnish. (ii) Set decade box to 4A. Adjust VR5 until you just get HY-TONE. Set to 5/1- ensure no HY-TONE . Seal VR5 with nail varnish. j RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 4/PAGE 8 : (J) R14 S.O.T . (BEFORE ECN 101 ONLY) Stay on 200A range . Connect decade box via croc clip leads, to R14 terminals - Set to approx. 10KA. Touch one probe to 0V - you should not get a tone. If you do, reduce decade box until tone just disappears. Touch other probe to 0V (after removing the first) . Ensure no tone. Again reduce decade box if necessary until tone just disappears. Note decade box reading. Connect nearest standard value resistor across R14, (probably best with E-Z clips first) . Again touch probes to 0V and ensure no tone. (If tone, reduce resistor value 1 value) . Solder R14 into place. ISS.l RESTRICTED AND COMMERCIAL IN CONFIDENCE 5. ENGINEERING CHANGE NOTES RELEVANT TO HY-TRAK 100D 5.1 101 - Solves Drift and CMRR Adjustments 5.2 102 - Earth Bonding 5.3 103 - Modified DPM Unit RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 5 /PAGE 1 5 . ENGINEERING CHANGE NOTES RELEVANT TO 100D 5.1 ECN 101 - Drift & CMRR Adjustments Problem : Elongated setting up time due to: (a) Selecting IC's 3, 4, & 5 for zero drift with volume. (b) Setting up CMRR pot. Solution for 1 : (a) Remove IC's 3 and 4 and associated IC sockets. (b) Replace resistors R21 and R22 with links. (c) Link IC3.3 to IC3.2. (d) Link IC4.3 to IC4.2. (e) Wire IC4.1 to IC5.1 (also see (g) below). (f) Wire IC4.5 to IC5.5 (also see (g) below) . (g) Insert Tant. capacitor 2.2uf 16v between IC4.1 and IC4.5 (polarity immaterial) . (h) Replace link idented -15V (near centre of PCB) with 470/1 l/4w 5% resistor. (j) Replace C5 with lOuf 16V electrolytic capacitor (polarity + to 0V connection) . (k) Cut track going to IC5 pin 4. (1) Wire from new C5 cap -ve to IC5.4. (m) Remove existing loudspeaker earth wire. Reroute from loudspeaker to 0V link (near centre of PCB) or as close as possible to transformer 0V. Solution for 2 : (a) Replace R26 (9K La) with lOKn. 1% lOOppm resistor. (b) Replace VRl with link. No CMRR adjustment is now required. 5.2 ECN 102 - Earth Bonding SAFETY WARNING TO ALL OMNITEST HY-TRAK 100D USERS THE HY-TRAK 100D SHOULD NOT BE USED UNTIL THE FOLLOWING MODIFICATIONS ARE CARRIED OUT. Problem : The front and rear panels of the HY-TRAK 100D are metal and are not earthed. As such this constitutes a potential health hazard and Omnitest Limited recommends that the following modifications are made to each instrument immediately. RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 5 /PAGE 2 Solution: (a) (b) (c) (d) (e) (f) (g) (h) (J) (k) (1) (m) (n) (P) (q) (r) Disconnect the instrument from the mains supply. Remove the probes from the front panel. Remove 4 countersunk screws from the base of the instrument. Lift off the lid and sides of the case complete with the handle . Remove knob from on/off volume pot. (This simply pulls off.) Unscrew the nut now revealed and slide on/off volume pot to the rear. It is not necessary to unsolder the wires to this pot. Add one 3/8" diameter solder tag to pot shaft, reposition in front panel and retighten retaining nut. We recommend the application of zinc paste to the front panel to prevent future oxidisation of the connection. Unsolder the Earth, Live and Neutral wires from the rear of the printed circuit board, adjacent to the mains transformer. Remove the rear panel. Drill and countersink a 4ba clearance hole in a suitable position. Solder a 4ba solder tag to themains earth wire (yellow/green) . Solder a yellow/ green wire in 16/0.2 gauge of suitable length to the earth point on the PCB. Terminate in a 4ba solder tag. Solder a yellow/green wire in 16/0.2 gauge of suitable length to the 3/8" solder tag on the on/off volume pot. Terminate in a 4ba solder tag. Bolt these three solder tags to the rear panel using a 4ba x i" countersunk screw, shakeproof washer and nut. Again the use of zinc paste on the rear panel is recommended. Resolder the Live (brown) and Neutral (blue) wires to the L and N terminals on the PCB. The connections should be sleeved with silicon rubber or heat-shrink sleeving. Replace the loudspeaker retaining screw situated near the centre of the PCB, with a M3 x 20mm countersunk nylon screw. Do not overtighten. Replace lid being careful to slide the front and rear panels into the appropriate grooves. Replace the 4 countersunk screws in the base. Replace the probes, reconnect the instrument to the mains and check the instrument still functions correctly. This modification scheme should not affect the calibration of the instrument at all. NOTICE If you do not wish to carry out this modification yourselves, .the instrument should be returned, suitably packed and post paid, to Omnitest Limited, where we shall be pleased to modify your instrument free of charge. There will, however, be a small fee to cover the return post and packing of the instrument. The instrument should be clearly labelled 'Returned for earth modification' . RESTRICTED AND COMMERCIAL IN CONFIDENCE ISS.l SECTION 5/PAGE 3 5.3 ECN 103 - Modified PPM Units This ECN only applies to any unit that had to use an Anders OEM2 to replace an OEM1 DPM. Problem : The OEM2 when used as a direct replacement for the OEMl causes a high current drain on the +4.7V supply. Dl, D2 and D3 inputs control the decimal point position on the LCD. These are actually inputs to a CMOS 4070 chip on the Anders OEM2. This chip has VDD at +4.7V (i.e. direct from our HY-TRAK +4.7V supply) but we now discover that VSS is not connected to -4.7V but to its own internal logic zero rail (about -2V) . Thus when we drive Dl , D2 or D3 to our logic zero of -4.7V, we are applying a negative voltage below the VSS of the chip which is turning on the input protection diodes and causing the high current drain on the VDD supply. Solution : We must connect pin 7 of IC10 and the -ve rail to switches 3 and 4 of the HY-TRAK to the logic zero rail of the OEM2. This involves 2 track cuts and two links to be fitted. The logic zero rail of the OEM's is available at the 'TEST' connection of the 0EM2. This is linked to the TST pin of the HY-TRAK. Rl and R2 on the HY-TRAK should now be lKn. - this gives us a potential 10mA supply which is ample for the 0EM2 and IC10 under normal conditions. Mod . Scheme : 1. Cut track at IC10 pin 7. 2. Cut -4.7V rail between switch 3 and VS pin. 3. Link TST pin to IC10 pin 7 and switch 3 formerly -4.7V rail pin. Application : (a) This mod scheme should be applied to all HY-TRAKs fitted with OEM2's, i.e. Serial No. 1110 onwards. (b) Any older unit that has to be repaired with a new DPM.